Mark 2 points along your track. It's simpler if they are on the same plane horizontally, but you can make it work otherwise.
Now you will decide how tall your shapes are. I forgot to screenshot this step, but you will want to draw where the corners of your shape meet. If there are no corners this is still possible, but good luck lad bc i'm not gonna take the time to explain THAT to you.
Now that you have the point where the corners, meet draw lines connecting the points.
Now that you have that, this is where you decide the rest of the dimensions of your shape. (Also in this step you help determine which shapes are going to overlap others. For example in the shape up above there is a shape beneath the larger one. This will be overlapping the one above it is above the horizon line (we are looking at the bottom of the shape) as opposed to the shape below the horizon line (we are looking at the top of it))
*I made the block below the horizon line more complex to help show how to do it with complex shapes. I added the guidelines for that and then drew it in the proper perspective.
In this next step you will take your newfound corners and connect them to the points that they aren't already connected to. In this step I deleted the grey lines to help show you, but you can keep them until the end if you'd like.
Where the grey lines meet FROM THE RESPECTIVE SHAPE that is your new corner. (Note that since I am doing a more complex shape below I am not done quite yet, we still need to determine how long it is on the bit that sticks out.
delete the gray lines, and I just fixed this little bit on the complex shape below, and you're done!